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<div class="titlepage"><div><div><h4 class="title">
<a name="range.reference.adaptors.general_requirements"></a><a class="link" href="general_requirements.html" title="General Requirements">General
        Requirements</a>
</h4></div></div></div>
<p>
          In the description of generator expressions, the following notation is
          used:
        </p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
              <code class="computeroutput"><span class="identifier">fwdRng</span></code> is an expression
              of a type <code class="computeroutput"><span class="identifier">R</span></code> that models
              <code class="computeroutput"><span class="identifier">ForwardRange</span></code>
            </li>
<li class="listitem">
              <code class="computeroutput"><span class="identifier">biRng</span></code> is an expression
              of a type <code class="computeroutput"><span class="identifier">R</span></code> that models
              <code class="computeroutput"><span class="identifier">BidirectionalRange</span></code>
            </li>
<li class="listitem">
              <code class="computeroutput"><span class="identifier">rndRng</span></code> is an expression
              of a type <code class="computeroutput"><span class="identifier">R</span></code> that models
              <code class="computeroutput"><span class="identifier">RandomAccessRange</span></code>
            </li>
<li class="listitem">
              <code class="computeroutput"><span class="identifier">pred</span></code> is an expression
              of a type that models <code class="computeroutput"><span class="identifier">UnaryPredicate</span></code>
            </li>
<li class="listitem">
              <code class="computeroutput"><span class="identifier">bi_pred</span></code> is an expression
              of a type that models <code class="computeroutput"><span class="identifier">BinaryPredicate</span></code>
            </li>
<li class="listitem">
              <code class="computeroutput"><span class="identifier">fun</span></code> is an expression
              of a type that models <code class="computeroutput"><span class="identifier">UnaryFunction</span></code>
            </li>
<li class="listitem">
              <code class="computeroutput"><span class="identifier">value</span></code>, <code class="computeroutput"><span class="identifier">new_value</span></code> and <code class="computeroutput"><span class="identifier">old_value</span></code>
              are objects convertible to <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">range_value</span><span class="special">&lt;</span><span class="identifier">R</span><span class="special">&gt;::</span><span class="identifier">type</span></code>
            </li>
<li class="listitem">
              <code class="computeroutput"><span class="identifier">n</span><span class="special">,</span><span class="identifier">m</span></code> are integer expressions convertible
              to <code class="computeroutput"><span class="identifier">range_difference</span><span class="special">&lt;</span><span class="identifier">R</span><span class="special">&gt;::</span><span class="identifier">type</span></code>
            </li>
</ul></div>
<p>
          Also note that <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">range_value</span><span class="special">&lt;</span><span class="identifier">R</span><span class="special">&gt;::</span><span class="identifier">type</span></code> must be implicitly convertible to
          the type arguments to <code class="computeroutput"><span class="identifier">pred</span></code>,
          <code class="computeroutput"><span class="identifier">bi_pred</span></code> and <code class="computeroutput"><span class="identifier">fun</span></code>.
        </p>
<p>
          Range Category in the following adaptor descriptions refers to the minimum
          range concept required by the range passed to the adaptor. The resultant
          range is a model of the same range concept as the input range unless specified
          otherwise.
        </p>
<p>
          Returned Range Category is the concept of the returned range. In some cases
          the returned range is of a lesser category than the range passed to the
          adaptor. For example, the <code class="computeroutput"><span class="identifier">filtered</span></code>
          adaptor returns only a <code class="computeroutput"><span class="identifier">ForwardRange</span></code>
          regardless of the input.
        </p>
<p>
          Furthermore, the following rules apply to any expression of the form
</p>
<pre class="programlisting"><span class="identifier">rng</span> <span class="special">|</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">adaptors</span><span class="special">::</span><span class="identifier">adaptor_generator</span>
</pre>
<p>
        </p>
<p>
          1. Applying <code class="computeroutput"><span class="keyword">operator</span><span class="special">|()</span></code>
          to a range <code class="computeroutput"><span class="identifier">R</span></code> (always left
          argument) and a range adapter <code class="computeroutput"><span class="identifier">RA</span></code>
          (always right argument) yields a new range type which may not conform to
          the same range concept as <code class="computeroutput"><span class="identifier">R</span></code>.
        </p>
<p>
          2. The return-type of <code class="computeroutput"><span class="keyword">operator</span><span class="special">|()</span></code> is otherwise unspecified.
        </p>
<p>
          3. <code class="computeroutput"><span class="keyword">operator</span><span class="special">|()</span></code>
          is found by Argument Dependent Lookup (ADL) because a range adaptor is
          implemented in namespace <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">adaptors</span></code>.
        </p>
<p>
          4. <code class="computeroutput"><span class="keyword">operator</span><span class="special">|()</span></code>
          is used to add new behaviour <span class="emphasis"><em><span class="bold"><strong>lazily</strong></span></em></span>
          and never modifies its left argument.
        </p>
<p>
          5. All iterators extracted from the left argument are extracted using qualified
          calls to <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">begin</span><span class="special">()</span></code>
          and <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">end</span><span class="special">()</span></code>.
        </p>
<p>
          6. In addition to the <code class="computeroutput"><span class="keyword">throw</span></code>-clauses
          below, <code class="computeroutput"><span class="keyword">operator</span><span class="special">|()</span></code>
          may throw exceptions as a result of copying iterators. If such copying
          cannot throw an exception, then neither can the whole expression.
        </p>
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<td align="right"><div class="copyright-footer">Copyright © 2003-2010 Thorsten Ottosen,
      Neil Groves<p>
        Distributed under the Boost Software License, Version 1.0. (See accompanying
        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
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